Combined paravertebral plexus block and parasacral sciatic block in healthy dogs

Objective To evaluate the effectiveness of paravertebral lumbar plexus block combined with parasacral sciatic block to anesthetize one hind limb in awake dogs. Study design Randomized, controlled, blinded experimental study. Animals Eight healthy mongrel dogs weighing 12.4 ± 4.5 kg and aged 7 ± 2.33 years. Methods After sedation with medetomidine, dogs received B1: bupivacaine 0.25%, 0.2 mL kg)1, B2: bupivacaine 0.5%, 0.2 mL kg)1, B3: bupivacaine 0.25% 0.4 mL kg)1, P1: NaCl 0.2 mL kg)1, P2: NaCl 0.4 mL kg)1. The lumbosacral plexus was blocked through a paravertebral block of the fourth, fifth and sixth lumbar nerves combined with a parasacral block. The relevant nerves were located using a nerve stimulator and injections of each treatment were administered. Degree and durations of sensory blockade were determined through the response to a Halsted clamp pressure on the skin innervated by the saphenous/femoral and lateral cutaneous femoral nerves (lumbar dermatomes) and by the peroneal and tibial nerves. The degree and duration of motor blockade was assessed evaluating the ability to walk normally and proprioception. Results P1 and P2 treatments did not show any grade of sensory or motor blockade. The B2 treatment produced a higher degree of sensory blockade compared to B1 and B3 for both lumbar and sciatic dermatomes. There was no significant difference in the degree of sensory blockade comparing B1 to B3. The B2 treatment had greater motor blockade compared to B1 and B3. The duration of sensory and motor blockade was longer in B2 compared to B1 and B3. Conclusion and clinical relevance When the nerve stimulator is used to perform the lumbosacral plexus block, the concentration of the bupivacaine has a more important role than the volume to produce a more solid and longer block.